JPH0522369A - Congestion preventing method for information network - Google Patents

Abstract

PURPOSE:To prevent information congestion of a reception station by increasing a delay of a delay timer in response to the reduction in a reception buffer resource due to increase in the communication quantity so as to send an acknowledge frame only with its expiration of time. CONSTITUTION:When congested communication is going to take place by various information frames 1a-1f from a station 1, the reception buffer resource is reduced. The reduction is monitored by a reception side station 2 and when the resource reaches a prescribed value or below, the delay in a delay time is increased. Then an acknowledge frame 2b is sent from the station 2 to the station 1 at the expiration of the timer whose delay time is increased and the station 2 processes resident reception information for the delay period. Through the constitution above, the occurrence of information congestion of the reception station is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an HDLC (Hifgh-level D) which is data link control standard data for an information network.
ata Link Control) and LL, which is a logical link control sublayer standard in a local area network (LAN).
In connection-oriented communication of C, the present invention relates to a method of preventing congestion of a communication station.

[0002]

2. Description of the Related Art FIGS. 2 and 3 are views for explaining a conventional connection-type communication in which a connection is set between two stations and communication is performed while confirming with a partner station.

FIGS. 2 and 3 show that communication is performed between the station 1 and the station 2, and that time elapses as it goes downward.

In the conventional connection type communication, the transmitting station can continuously transmit a plurality of information frames without waiting for confirmation of the partner station, and the partner station collects confirmations of the plurality of information frames at the same time. Can be returned to. The maximum number of transmission windows is the number of information frames that can be continuously transmitted without waiting for confirmation of the partner station, and the frame returned for confirmation is called a confirmation frame.

The receiving station starts a timer (delay timer) at the time of starting the reception of the information frame, and confirms when the timer times out or when the number of received information frames exceeds a preset maximum number of reception windows. The frame was returned to the transmitting station. The value of the delay timer must be smaller than the response monitoring timer (ACK timer) value of the partner station.

FIG. 2 shows that the maximum number of transmission windows of station 1 is 3,
When the maximum number of receiving windows of station 2 is set to 3, station 2
Shows the case where the confirmation frame 2 is transmitted to the station 1 because three information frames 1a to 1c have been received before the delay timer times out.

FIG. 3 shows that the maximum number of transmission windows of station 1 is 4,
When the maximum number of receiving windows of station 2 is set to 4, station 2
Shows that the confirmation frame 2 is transmitted to the station 1 because the delay timer has timed out before receiving the four information frames.

[0008]

FIG. 4 is a diagram for explaining the problems in the above conventional technique. In FIG. 4, as an example, the maximum number of transmission windows of the station 1 is 3, the maximum number of reception windows of the station 2 is 3, and the delay timer value is Td.
It is assumed that the information frame is continuously transmitted to the station 2.

When the station 1 continuously transmits the information frames, the station 2 receives the maximum number of information windows 1a to 1c before the delay timer times out and transmits the confirmation frame 2a.

The station 1 which has received the confirmation frame 2a transmits the next information frames 1d to 1f. However, if the processing of the first information frames 1a to 1c may not be completed during the time Tx for receiving the first information frame 1a to the second information frame 1d, a congestion state occurs due to the repetition of such a sequence. Come to do.

When a congestion state occurs, the station 2 temporarily transmits a frame indicating that it cannot be received to the station 1, and the station 1 stops transmitting the information frame until the congestion state is released.

Although the delay timer can reduce the number of transmissions of confirmation frames to reduce the number of frames in the network, it cannot prevent the congestion state.

An object of the present invention is to provide a congestion prevention method for an information network, which can prevent the occurrence of the above congestion state.

[0014]

In order to solve the above problems, the receiving station monitors the receiving buffer resource amount of the information frame in its own station, and when it falls below a predetermined value, the delay amount of the delay timer. Is increased, and thereafter the confirmation frame is transmitted to the transmitting station only by the timeout of the delay timer.

[0015]

When the communication becomes congested, the reception buffer resource amount decreases. Therefore, when the reception buffer resource amount becomes less than a predetermined value, the delay amount of the delay timer is increased and the confirmation frame is transmitted only by the timeout, and the transmitting station Performs the next transmission upon receipt of this confirmation frame, during which the receiving station processes the received information.

[0016]

1 is an example of a transmission sequence diagram of an information frame in which congestion of an information network is prevented according to the present invention.

In FIG. 1, since the receiving station temporarily stores the received information frame in the receiving buffer, it can be determined that the communication is not congested when the number of free receiving buffers is more than a predetermined value. Similarly, the delay timer value and the maximum number of windows are set.

Further, if the reception amount increases, the number of free buffers for reception decreases, and if it falls below a predetermined value, communication congestion may occur. Therefore, the delay timer value of the receiving station is increased, and the next timer is set only by the timeout. The confirmation frame is transmitted, and the transmission of the confirmation frame according to the number of received information frames is stopped. Therefore, the maximum number of receiving windows is reset to infinity.

Since the transmitting station does not perform the next transmission until it receives the confirmation frame, the receiving station can process the increased reception information during this period to recover the number of free reception buffers.

Further, the delay timer value of the receiving station is set to be large within the value of the response monitoring timer (ACK timer) on the transmitting station side.

As an example, in FIG. 1, the response monitoring timer of the station 1 is 3 seconds, the maximum number of transmission windows is 3, the initial value of the delay timer of the station 2 is 500 ms, and the maximum number of reception windows is 3.

Therefore, the station 2 receives the station 1 within 500 ms.
When the three information frames 1a to 1c are received, the confirmation frame 2a is transmitted to the station 1.

While repeating this sequence,
The station 2 determines that a congestion state may occur when the number of free reception buffers of the station 2 becomes less than 40% of the total number of reception buffers, and the station 2 changes the delay timer value to 2.5 seconds,
Due to this timeout, the confirmation frame 2b is transmitted.

Station 1 cannot transmit the next information frame until it receives confirmation frame 2b from station 2. But,
Since the delay timer value of 2.5 seconds is smaller than the ACK timer value of 3 seconds, the station 1 can receive the confirmation frame 12b. However, it is not necessary to perform error recovery processing such as inquiring about the status of the station 2.

On the other hand, since the station 2 does not receive the information frame for at least 2 seconds after receiving the three information frames, it processes the received information which has been delayed during this period and releases the receiving buffer being processed. Can prevent the occurrence of congestion.

The increased delay timer value is returned to the original value when the resource amount of the receiving station such as the receiving buffer is restored to a predetermined level. For example, when the number of free reception buffers of the station 2 is recovered to, for example, 60% or more of the total number of reception buffers, the station 2 returns the delay timer value to 500 ms to set the maximum number of reception windows to 3, and the delay timer and the reception window. The number-based confirmation frame transmission is used again.

Although the delay timer value is changed according to the number of free buffers for reception in the above embodiment, the delay timer value can be changed according to the states of other resources. Although the value of the delay timer is changed from 500 ms to 2.5 seconds, it can be changed stepwise according to the amount of resources. For example, the delay timer value is doubled each time the resource amount decreases by a fixed value.

[0028]

In accordance with the decrease in the receiving buffer resource amount of the receiving station due to the increase of the communication amount, the delay amount of the delay timer is increased and the confirmation frame is transmitted only by the timeout, and the transmitting station transmits the confirmation frame. Since the next transmission is stopped until it is received, the receiving station can process the increased received information during this period to prevent the occurrence of congestion.

[Brief description of drawings]

FIG. 1 is a transmission sequence diagram of an information frame according to the present invention.

FIG. 2 is a transmission sequence diagram of a conventional information frame.

FIG. 3 is a transmission sequence diagram of a conventional information frame.

FIG. 4 is a transmission sequence diagram of a conventional information frame.

[Explanation of symbols]

 1a to 1i Each information frame 2a to 2c Each confirmation frame

Claims (1)

Claim: What is claimed is: 1. A transmitting station continuously transmits an information frame within a maximum number of transmission windows to a receiving station, and the receiving station starts a delay timer at the start of reception of the information frame to delay the delay. When the timer times out or the number of information frames received reaches the maximum number of reception windows, a frame confirming the reception of information frames up to that point is sent to the transmitting station, and the transmitting station receives the above confirmation frame and then In a network that establishes a connection between two stations that transmits information frames within the maximum number of transmission windows below and performs communication while confirming with the partner station, the receiving station is the buffer for receiving information frames within itself. The system further comprises means for monitoring the resource amount and means for increasing the delay amount of the delay timer when the resource amount falls below a predetermined value. A method for preventing congestion of an information network according to claim 1, wherein the confirmation frame is transmitted only by the delay timer time-out after the delay amount of the delay timer increases.